Want to install latest stock rom before I dump sprint

I get horrible signal all over the San Francisco area. Inside my home half the time I can't even make a call. Before I just give up on Sprint I thought I'd try installing the latest stock rom and whatever updates it has and see if that helps.

Can anyone tell me where I can find the latest ota update for the Sprint note 4? Would prefer to keep it rooted.

And if anyone has any other suggestions to improve the signal on the phone, I'm all ears.

Thanks